Since inorganic ion exchangers are excellent in terms of heat resistance and radiation resistance compared with ion exchange resins, their application to the ion exchange treatment, separation, concentration, and purification of strongly radioactive substances, etc. in high temperature water has been expected for a long time. Among them, antimony pentoxide [Sb2O5·kH2O (here, k is a positive number of 4 or less)], tin antimonate [SnO2·bSb2O5·lH2O (here, b is a positive number and l is 0 or a positive number)], titanium antimonate [TiO2·cSb2O5·mH2O (here, c is a positive number of 0.6 or less and m is 0 or a positive number)], etc. have been considered to be promising, and various studies have been carried out (e.g. Patent Documents 1, 2, 3, and 4).